This invention relates to an apparatus for discriminating the physical condition of a paper-like material.
When circulated, the paper-like material such as bank notes, securities and cheques, sometimes meet problems such as fading of the original color of the material, contamination e.g., depositing of stains, and the printing ink drips from the material.
Various types of the apparatus as described in the preamble that may discriminate such stains deposited on the paper-like material have been proposed. For example, in the conventional apparatus the print patterns of the bank notes are optically picked up and then converted into the corresponding electrical signal, and thereafter the output voltage level of the electrical signal is electrically processed so as to determine the contamination of the bank notes. Such a conventional apparatus is disadvantageous in that it cannot reliably discriminate the print pattern of the notes whose output signal level changes sharply.
It is therefore a primary object of the invention to provide an apparatus which can discriminate exactly defects such as contamination without adverse influence from their print patterns.
It is a secondary object of the invention to provide an apparatus for discriminating defects in which the degree of the defect e.g., soiled material, namely a threshold level of variations on the output voltage level is presettable.
It is a third object of the invention to provide an apparatus for discriminating defects in which the area of the defect, e.g., soil of the material, namely a threshold level of variation duration periods on the output voltage level is presettable.